Lecture 9 Flashcards
Binocular Cues : Oculomotor Depth Cues
Absolute depth perception
Vergence
Eye convergence for near objects, divergence for distant ones
Accommodation
Ciliary muscles adjust lens shape for focus
Vergence Limit
Reliable up to 2m
Accommodation Limit
Active up to 6m (beyond this is optical infinity)
Binocular Cues : Stereopsis
The rich impression of depth that we get from seeing with both eyes
Binocular Disparity
The slight difference in the images perceived by each eye due to their horizontal separation, which the brain uses to calculate depth and perceive a three-dimensional view of the environment
-Stereopsis relies on this
Vieth-Muller Circle
An imaginary geometric circle in visual space that passes through the point of fixation and the optical centers of both eyes
-It represents the theoretical locations of objects that produce corresponding retinal points in both eyes, resulting in no binocular disparity and thus appearing at the same depth as the fixation point
Horopter
The spatial region in visual space where objects project images onto corresponding retinal points in both eyes
-Objects appear to be at the same depth as the point of fixation and are perceived without binocular disparity
Panum’s Fusional Area
The region in visual space around the horopter where slight binocular disparities can still be fused by the brain to produce a single, unified perception of depth
-Objects within this area are seen as single despite small differences in the images projected onto the retinas of each eye
Crossed Disparity
Occurs when object is closer to you than the point of fixation
Explanation of Crossed Disparity
The image of the object falls on the outer (temporal) side of the retina in both eyes
-From the left eye’s view, it is located to the right of the fixation point, and from the right eye’s view, it is located to the left of the fixation point
Result in Perception of Crossed Disparity
The brain interprets crossed disparity as indicating that the object is in front of the fixation point and closer to you in three-dimensional space
Uncrossed Disparity
Occurs when an object is farther away from you than the point of fixation
Explanation of Uncrossed Disparity
The image of the object falls on the inner (nasal) side of the retina in both eyes
-From the left eye’s view, it is located to the left of the fixation point, and from the right eye’s view, it is located to the right of the fixation point
Result in Perception of Uncrossed Disparity
The brain interprets uncrossed disparity as indicating that the object is behind the fixation point and farther away in three-dimensional space
Stereoscope
A device for presenting one image to one eye and another image to the other eye
-For movies to appear 3D, each eye must receive a slightly different view of the scene (just like in real life)
Correspondance Problem
In binocular vision, the problem of figuring out which bit of the image in the left eye should be matched with which bit in the right eye
Random Dot Stereogram
A visual pattern consisting of two images made up of random dots
-When viewed with both eyes, the two images create the illusion of a three-dimensional shape or object floating in space
3 Steps of Random Dot Stereogram
- Generation
- Disparity
- Perception
Generation
-Two similar random-dot patterns are created
-A section of one pattern is shifted slightly horizontally relative to the corresponding section in the other pattern
Disparity
-The horizontal shift creates binocular disparity when the two images are viewed together
-This disparity mimics the differences in the images seen by the left and right eyes in real-world 3D viewing
Perception
-When each eye views one image, the brain fuses the two patterns
-The shifted section appears as a 3D object or surface due to the brain’s interpretation of the disparity
Binocular Rivalry
The competition between the two eyes for control of visual perception, which is evident when completely different stimuli are presented to the two eyes
